Screw-on annular rings for die cast beryllium copper plunger tips

ABSTRACT

A metal plunger tip has a forward generally cylindrical section having a leading relatively flat forward end and enlarging at its rearward end to a first land. A middle generally circular threaded section spans between the first land and a second generally larger land at its rearward section. A rearward generally cylindrical section of larger diameter spans between the second land a its rear surface that terminates with a section for attachment to an externally threaded push rod. There is an interior cooling cavity in the plunger tip terminating with a rear internally threaded section for mating with an externally threaded push rod. The metal plunger tip can be made from beryllium copper. The metal plunger tip may have a leading chamfered edge. A metal wear ring can be screwed onto the metal plunger tip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of provisional application Ser. No. 61/640,017, filed Apr. 30, 2012, the disclosure of which is expressly incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

The present invention generally relates to plunger tips such as are disclosed in U.S. Pat. No. 4,732,206 and more particularly to an improved method for adding annular rings to plunger tips, as shown in U.S. Pat. Nos. 5,048,592 and 5,233,912.

The desired plunger tips may be cast from a beryllium-copper alloy. These plunger tips are useful in the die casting of aluminum, zinc, magnesium, and other metals and alloys, which can be injected into a mold cavity with the aid of the plunger tips.

A variety of plunger tip designs are known in the art, such as shown in, for example, U.S. Pat. Nos. 4,667,729, 4,623,015, 4,886,107, 6,311,761, 4,311,185, and 4,334,575). Most of these plunger tips consist of a circular annular body mounted onto a reduced area, annular rectangular (square) body. The plunger tip is internally threaded up to the circular annular body for insertion of an externally threaded plunger rod. The rectangular (square) body enables the plunger rod to be screwed into the plunger tip.

U.S. Pat. Nos. 5,048,592 and 5,233,912 disclose a Ring-Plunger System to include a sealing ring, a cap, and a plunger body. In particular, the '592 patent in its broadest aspect claims a body (holder) and a cap (plunger). A sealing ring can be added to this combination. The '912 patent improves upon how the body and cap are interconnected.

U.S. Pat. No. 4,667,729 discloses a shot tip for a cold chamber die casting machine wherein the head 24 is hollowed out to provide an internal coolant chamber 30 the left hand portion of which is provided with internal threads 31 to engage with the external mating threads of a plunger body 40. A tube 32 extends axially into the chamber within the head 24 to form a first coolant flow path between the external surface of the tube 32 and the interior surfaces of the head 24 and the plunger body 40. Tube 32 defines a second coolant flow path within the tube 32 itself. The first flow path is inbound and the second flow path is outbound and these flow directions are important to the operation of the device.

U.S. Pat. No. 3,920,099 discloses a plunger which comprises a shank portion 35, provided at its inner end, disposed within the shot sleeve 10, with external threads 36 and at its opposite end with an outwardly directed annular flange 37 by means of which the plunger may be operatively mounted on the end of the rod 12, as for example by means of a locking collar or ring 38 suitably rigidly secured to the end structure of the rod 12. The operating end of the piston or plunger 11 is formed by a hollow cylindrical head member 39 having a chamber 40 therein and is provided with a bore 41 having internal threads cooperable with the threads 36 on the adjacent end of the shank member 35. The transverse wall 42 of the head member 39, forming the inner end wall of the plunger 11, is provided with an axially extending bore 43 therein which, in the embodiment of the invention illustrated, terminates at its outer end in an outwardly flaring valve seat 44 for cooperation with the head 45 of a valve member, indicated generally by the numeral 46, having a stem portion 47 extending inwardly from the head 45, with the stem 47 extending into the coaxially extending bore 48 of the hollow shank member 35.

U.S. Pat. No. 4,664,173 discloses a shot rod 100 having an externally threaded portion for receiving an internally threaded plunger tip 30 having a contact face 31 which is used to contact molten metal for moving the metal through a shot sleeve or cylinder into a die cavity. The plunger tip 30 is reciprocally movable within the shot sleeve or cylinder in a manner similar to a piston and cylinder.

U.S. Pat. No. 6,752,197 discloses an injector particularly for a vacuum die-casting apparatus wherein the injector 10 is constituted by an injector body 12 which has, in an upward region, at least one first opening 13 for loading molten metallic material, generally designated by the reference numeral 18, by means of a ladle 14, and at least one second opening for introducing/aspirating protective gas 28 and for generating a vacuum, which is connected to ducts, generally designated by the reference numeral 16, which are part of a pressurized circuit. The injector body 12 is further provided with a chamber 17 for containing the molten material 18 and for the sliding of a piston 19 for injecting the material 18 into dies 20. Plate 11, a chamber housing 12 having plunger chamber 13 and pouring or feed slot 14, a hollow plunger or ram 15 connected at one end to a piston rod 16 and at the other end carrying a dummy block 17. Water cooling connections 18 are provided on the plunger 15. The dummy block 17 is made up of an inner shell nut 20 having an axial bore 21 threaded to receive the threaded male end 15 a of the plunger 15. The nut 20 is provided with flats 22 at one end of its outer periphery to receive a wrench and with threads 23. An outer cylindrical hollow shell 24 is threaded internally at one end to receive the threads 23 of the nut 20. The other end is closed by end wall 24 a. A radially inwardly extending flange or stop is provided intermediate the inner wall 25 of the shell against which the end 20 a of nut 20 abuts. The end 20 a of nut 20 is provided with a groove 20 b carrying an elastomer O-ring 30 which seals the two parts to prevent escape of cooling water. A lock screw 26 is threaded through the end wall of nut 20 to engage against the shell 24 to prevent relative rotation of the shell and nut. It is obvious from the structure that the cooling fluid in the plunger will pass through nut 20 into the interior of shell 24 and contact end wall 24 a to cool and protect the whole dummy block structure. When the shell 24 is worn it is replaced on nut 20 rather than discarding the whole block assembly as has been the practice in the past.

U.S. Pat. No. 6,311,761 discloses a plunger tip for die casting wherein the plunger tip 1 comprises an annular body 15 having a rearward end portion designated in its entirety by the reference numeral 17 of such peripheral outline as to be reciprocal in the shot sleeve 5. The latter having a circular bore 5 a, said rearward end portion 17 has a forward formation 19 of circular outline of such diameter as to have a relatively close sliding fit in the shot sleeve and an integral rearward formation 21 of polygonal and more specifically hexagonal outline. The body 15 has an integral cylindrical externally threaded hollow extension 23 extending forward from the said rearward end portion 17 of the body 15 coaxial therewith and of smaller peripheral outline than rearward end portion 17 (smaller external diameter than the diameter of the circular forward formation 19). The external threading of extension is indicated at 25. The rearward end portion 17 of the body 15 has a rear face 27, more particularly a flat rear face, and the body has a part-spherical recess 29, more particularly a hemispherical recess, in said rear face. The hollow 31 of the externally threaded extension 23 extends from recess 29 to the forward end 33 of the extension, being primarily of conical or tapered form divergent generally from the recess to the forward end. As shown it has a very short cylindrical rear end portion 35 (the small diameter end of the hollow 31) coming off the recess 29.

BRIEF SUMMARY OF THE INVENTION

A metal plunger tip has a forward generally cylindrical section having a leading relatively flat forward end and enlarging at its rearward end to a first land. A middle generally circular threaded section spans between the first land and a second generally larger land at its rearward section. A rearward generally cylindrical section of larger diameter spans between the second land a its rear surface that terminates with a section for attachment to an externally threaded push rod. There is an interior cooling cavity in the plunger tip terminating with a rear internally threaded section for mating with an externally threaded push rod. The metal plunger tip can be made from beryllium copper. The metal plunger tip may have a leading chamfered edge. A metal wear ring can be screwed onto the metal plunger tip.

The metal wear ring is a generally circular annulus having a forward generally smooth interior and an internally threaded rearward section with a first wear ring land therebetween. The internally threaded rearward section terminates with a second wear ring land. The metal wear ring screws onto said metal plunger tip with said the plunger tip and wear ring lands mating, and the second plunger tip and wear ring lands mating.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is an isometric view of the screw on plunger tip and wear ring;

FIG. 2 is an isometric view of the screw on plunger tip of FIG. 1 with the wear ring screwed onto it; and

FIG. 3 is an isometric view of the screw on plunger tip of FIG. 1 with the wear ring partially screwed onto it;

FIG. 4 is a side view of the screw on plunger tip of FIG. 1;

FIG. 5 is a front-end view of the screw on plunger tip of FIG. 1;

FIG. 6 is a rear end view of the screw on plunger tip of FIG. 1;

FIG. 7 is a sectional view taken along line 7-7 of FIG. 5;

FIG. 8 is a side view of the wear ring of FIG. 1;

FIG. 9 is a front-end view of the wear ring of FIG. 8;

FIG. 10 is a rear end view of the wear ring of FIG. 8;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 10; and

FIG. 12 is a sectional view of an alternative screw-on plunger tip embodiment.

The drawings will be described in further detail below.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially to FIGS. 1, 4, 5, 6, and 7, a plunger tip, 10, as disclosed herein is seen in isometric view. Plunger tip 10 has 3 distinct sections: a threaded section, 12; an upper narrowed diameter smooth section, 14; and a normal, lower, smooth plunger diameter section, 22. An upper land, 18, is formed between the top of threaded section 20 and narrower upper section 14. A lower land, 20, is formed between the bottom of threaded section 12 and lower section 22. From lower, standard diameter section 22 to threaded section 12 to upper section 14, each succeeding section from bottom to top narrows in diameter. The lands are formed due to such diameter change.

A wear ring, 24, is seen ready for installation to plunger tip 10 in FIGS. 1, 8, 9, 10, and 11, also. Wear ring 24 has outer flutes, such as flutes 26, for debris removal in use. Such flutes also can be used with a spanner wrench for installation and removal of the wear ring. Importantly, the inner annular wall of wear ring 24 tapers from an upper smooth section, 30, to a lower threaded section, 28. Wear ring 24 has a land, 32 between smooth section 30 and threaded section 32; and a land, 34, terminating threaded section 32.

When wear ring 24 is installed on plunger tip 10, such as is depicted in FIG. 2, wear ring section 30 mates with plunger section 14 and wear ring threaded section 28 maters with plunger tip threaded section 12. In particular, flange 34 on wear ring 24 mates with flange 20 of screw on plunger tip 10. Flange 32 on wear ring 24 mates with flange 18 of screw on plunger tip 10. Wear ring 24, hence, is supported not only by the threads, but also by both of the lands on plunger tip 10. Such extra support enables wear ring 24 to take the forces under high temperature in use, such as with molten aluminum. This additional support can be seen also in FIG. 3, which shows a partial installation of wear ring 24 onto plunger tip 10.

An alternative embodiment of the screw on plunger tip is seen in FIG. 12. In particular, a screw on plunger tip, 40, is seen in cross-section. Plunger tip 40 has a chamfered leading edge, 44, and leading flange, 48, that mates to land 32, of wear ring 24. A threaded section, 42, screws with threaded section 28 of wear ring 24. While chamfer leading edge 44 is 45°, it could be of lesser or greater angle.

Outwardly from a land, 50, is a smooth larger diameter section, 52. Land 50 mates with land 34 of wear ring 24. The remaining construction of plunger tip 40 is like that of plunger tip 10.

Materials of construction for the plunger tip and wear ring can be steel, alloys (e.g., beryllium copper) or any other useful material.

While the invention has been described with reference to a preferred embodiment, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In this application all units are in the metric system and all amounts and percentages are by weight, unless otherwise expressly indicated. Also, all citations referred herein are expressly incorporated herein by reference. 

I claim:
 1. A metal plunger tip, which comprises: a forward generally cylindrical section having a leading relatively flat forward end and enlarging at its rearward end to a first land, a middle generally circular threaded section spanning between said first land and a second generally larger land at its rearward section, a rearward generally cylindrical section of larger diameter spanning between said second land a its rear surface that terminates with a section for attachment to an externally threaded push rod, there being am interior cooling cavity in said plunger tip terminating with a rear internally threaded section for mating with an externally threaded push rod.
 2. The metal plunger tip of claim 1, made from beryllium copper.
 3. The metal plunger tip of claim 1 having a leading chamfered edge.
 4. The metal plunger tip of claim 3, wherein said chamfered edge is at about a 45° angle.
 5. A metal plunger tip and wear ring assembly, which comprises: a metal plunger tip comprising: (a) a forward generally cylindrical section having a leading relatively flat forward end and enlarging at its rearward end to a first plunger tip land, a middle generally circular threaded section spanning between said first plunger tip land and a second generally larger plunger tip land at its rearward section, a rearward generally cylindrical section of larger diameter spanning between said second land a its rear surface that terminates with a section for attachment to an externally threaded push rod, there being am interior cooling cavity in said plunger tip terminating with a rear internally threaded section for mating with an externally threaded push rod; and a metal wear ring comprising: (b) a generally circular annulus having a forward generally smooth interior and an internally threaded rearward section with a first wear ring land therebetween, said internally threaded rearward section terminating with a second wear ring land; said metal wear ring screwing onto said metal plunger tip with said first plunger tip and wear ring lands mating, and said second plunger tip and wear ring lands mating.
 6. The metal plunger tip of claim 5, made from beryllium copper.
 7. The metal plunger tip of claim 5 having a leading chamfered edge.
 8. The metal plunger tip of claim 7, wherein said chamfered edge is at about a 45° angle. 